Validity and reliability of results of epidemiological studies for the estimation of the radiation included lung cancer risk

Several studies pertaining to the risk coefficients for the internal - and external exposure of the lung are critically evaluated. For radiation protection purposes, ICRP assumes risk coefficients in the range of 5-15 per 106 PY per WLM for internal and 20 per 104 per Sv for external lung exposure. The risk coefficient for internal lung exposure, based on results from investigations on American and Czech uranium miners, is in agreement with results from more recent epidemiological studies within the given range. The risk coefficient of 20 per 104 per Sv assumed by ICRP for external lung exposure based on results of studies on A-bomb survivors up to 1977, gives information only on the integral lung cancer frequency per dose unit. Assuming a constant annual lung cancer incidence (absolute risk) of up to 25 years after exposure, a coefficient of 0,8 per 104 PY per Sv will result. This value is in agreement with recent results from studies on A-bomb survivors and results from ankylosing spondylitis studies. There are indications, however, that the radiation induced lung cancer risk in particular is proportional to the spontaneous lung cancer risk (relative risk model). This leads to the conclusion that the risk coefficient given by ICRP for an observation period of 25 years would underestimate the life time risk, i.e. with longer observation periods in the relevant epidemiological studies, the risk coefficients gained from those studies would become increasingly different from currently assumed ICRP values. 1 ref., 1 tab. (Author)